Grease a 9x13-inch baking dish. Spread the bread cubes across the bottom. Sprinkle the cheese and bacon over the bread cubes.
In large mixing bowl, combine the egg, milk, mustard, and black pepper. Pour the egg mixture over the bread and cheese mixture.
Cover and refrigerate overnight.
In the morning, preheat the oven to 350F. Bake for 45 minutes to 1 hour, or until puffy, and a tester inserted comes out clean.
Serve hot or warm.
Note: To freeze: Once assembled, place the dish, covered, in the freezer. Thaw in the refrigerator overnight before proceeding with the baking step.To prepare individual servings: divide the ingredients among 8 large ramekins. Proceed with the recipe, adjusting the baking time to 20 to 25 minutes.Promptly store leftovers in an airtight container in the refrigerator, for up to 3 days.Nutritional values are approximate and based on 1/8 the recipe.